Johk thomson



J. THOMSON.

ELECTRIC FURNACE FOR REDUCING OXlDiZED ZINC CONCENTRATES BY CARBON.

APPLlCATlON FILED JAN.2I, I919.

' Patented Nov. 11, 1919.

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\NVENTOR BYAJ ATTORNEY CM W J. THOMSON.

ELECTRIC FURNACE FOR REDUCING OXIDIZED ZINC CONCENTRATES BY CARBON.

APPLICATION FILED JAN. 27. I919- 1,321 683. Patented N0v.11,1919

4SHEETS-SHEET a.

' INVENTOR 2 R BYLJ ATTORNEY v gnW -o J. THOMSON.

ELECTRIC FURNACE FOR REDUCING OXIDIZED zmc CONCENTRATES BY CARBON. APPLICATION FILED JAN.2I.19\9.

1 321,683. Patented Nov. 11, 1919.

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Specification of Letters Patent. NOV. 11, 1919.

Application filed January 27, 1919. SerialNo. 273,234. I :1

useful Improvements in Electric Furnaces.

for Reducing Oxidized Zinc Concentrates by Carbon, of which the following 1s a spec1- fication.

This is an invention in electric furnaces for reducing oxidized zinc concentrates by carbon, according to the classical formula ZnO+C:Zn+CO, and the dominant objects thereof are to simplify and minimize the cost of construction and maintenance and to substantially increase the efficiency over that of previous practice.

As herein employed, oxidized zinc concentrate (ZnO) may either be understood to mean the usual mill-concentrate whose major ingredient is metallic, the remainder being 'gangue; or it may relate to i-gneously produced oxid of zinc Whose recoverable metallic content may approximate the theoretical limit, about 80 percentum, the remainder being oxygen; and the reducing agent, carbon, refers to granulated coal or coke containing a variable quantity of inert, residual matter. The object of the foregoing academic statement is to particularly accentuate the important correlative fact that if the charge to bereduced is composed of relatively low-grades of oxid and carbon the resulting residuum, usually in the form of ash and sinter, will be a maximum, while if the charge were composed of balanced reacting volumes of pure o-xid and pure carbon, there would then be no residual matter whatever. i I

The ZnO+C reaction primarily becomes active at or about a. temperature -of 1,000 C.; but the rapidity thereof is-a function of .two factors: the quantitative supply of heatunits and the freedom with which the evolved, vaporized products (Zn+CO) can escape from the charge-material. Thus, if the fame and gas are so confined as to pro duce baclo-pressure the intensity of the react on in: e thereby be more or less diminished or even be wholly suspended. The

sum of the pressure necessary to e'fiect this matresult is relatively qu te nominal.-

Tl'iercfore, in these circumstances, if heat units are rapidly transferred and are not withequal rapidity absorbed by-the .re-

action,- destr'uctive hot-spots will be deve'loped and energy is uselesslydissipated.

Again, when ZnO is highlyheated it becomes a relatively.efi'ectiyeficoriductor of "electricity; "andthefailm'e to take cog- I nizance of this phenomenon hashitherto been a potent causelof failure, as when a reactive chargehas bee'n placed incontact with a bed of carbon, serving asa resistor.

In the drawings, whichdepicta preferred practical realization of :this invention and form a part of this specification Figure, 1 is a vertical, tral'isversecenter section of thefurn'ace, viewed as denoted by arrows A, A;- I I Fig. 2 is a yertical, longitudinal'center section, according toarroWsB, B; Fig. 3 is ajhori'zonltal, sectional plan, along the plan'e indicat'ed-by arrows G; C;

Fig. 4 is" a diagraminatic reproduction,

of Fig. 1 for-the purpose of illustrating the thermaey of the operation.

The principal elements of the structure are as follows: I

D is the brick-work which forms the base; E, E, are the side-Walls; F, F, are the end walls; H is the ro0f; I isthe reaction chamber and J is a monolithic carl in resistor disposed along the longitudinal axis of'the chamber, whose terminals, '5, "6, are con nected to a source of energy, symbolically denoted by K. 1

Tlic resistor is of'the zig-zag type and comprises two parallel limbs 7, separated by a vertical space 8, except that their inner ends are joined by a connector, 9, whereby the electric circuit is in series. The said limbs are preferably formed frbm rectanular slabs, set edge-Wise, vertically, resting on refractory supports within the chamber, as 10,12,133. As a unitary element, the resistor herein depicted is characterized by having its narrower sides beveled, 14, 1 5,whcreby its cur rent-density and. corresponding lieat-eniis sivity are greater along the faces and the bevels which are presented toward the object to be heated, or is primarily shown in applicants Patent No. 1,193,633 ofv acteristic of the resistor. which is pffsignal importance consists in filling its slits and tricity, immune to oxidization and non-reactivewith carbon; also in usually curing the protective coating, by means of heat developed within the resistor itself, and carrying the temperature to a higher point than that at which it is eventually to be used, or as is set forth in applicants copending application Serial No. 228,908, -filed April 16, 1918.

The preferred material, or materials, referrd to in the foregoingpara graph, is silicon carbid, or fused aluminum oxid, primarily combined with an element capable of being more or less fluxed at a relatively high temperature; and the said fiuxing ele ment should preferably be, in the present instance, of a -silicious base, in that there will be more or less of physical contact with oxid of zinc. 4

The operative elements and the maneuver are as follows: The furnace-chamber is more or less filled with a reacting charge which surrounds the resistor, the material to be smelted being inserted through a relatively narrow longitudinal slot, 16. This opening is normally closed by a valve-plate, L, preferably covered by charge-material, as denoted by the broken line 17, placed in a recess, M, on top of the furnace. The valve-plate has a rib, 18, whereby it may be conveniently engaged by a hooked-rod to be drawn or slid over, as to the position indicated by the dotted outline, 19, thereby opening the slot and permitting the superimposed. material to flow into the chamber.

In this wise, the hot inner surface of the.

valverplate is not exposed to atmosphere; while the overlying concentrate serves to seal the roof-joints and is somewhatpreheated.

The upper portion of the space between the limbs of the resistor is inclosed by a molded refractory, N, to be designated a deflector, resting upon shoulders, 20, 21 and is provided with a seriesof transverse ports,

In each side-wall, along the lower zone of the chamber, a series of extraction ports, 23, 2 1, are formed which are normally closed by free refractory plugs, as 25, and for their convenient insertion and removal handles, as 26, are provided.

The inner surface of the roof is upwardly beveled, as 27, 28, right and left toward the center, whereby to 'refract heat, received from the resistor, downwardly into the side reaches of the chamber.

When the charge passes down through the roof-slot, it first impinges upon the defiector and runs olf equally on either side.

In one of the end walls, near the top of the chamber, is a molded throat, P, through which the va orized products of the rcac-' tion tZn+C escape to a condenser, the latter not being shown; but a preferred de sign would be developed from that shown in the patent already cited together with subsequent Patents Numbers 1,219,193 of" in the deflector, N, and thence down be-- tween the limbs of the resistor, there will yet be some unfilled space beneath its lower bevels. Heat will then be transferred to the charge by direct conduction, as denoted by arrows a and the evolved fume and gas will flow through the comparatively shallow portion of the charge, with a minimum of restriction, as arrows b, c; from beneath the vaporized products will pass freely upwardly, as arrow d, and thence through the deflector ports, as arrows e, to condenserthroat, P.

When, however, the charge will have been partially reduced, as indicated on the right hand side by the broken line 32, reactive.

heat will then be transferred by radiation as arrows h and m, and by heat from the upper bevels of the resistor refracted directly downwardly from the sloped roof, as arrows n.

In the foregoing circumstances, the inner surfaces of'the charge are the hottest,

from whence the zinc-fume and monoxid of carbon pass off with the utmost freedom,- as and when evolved and with all the rapid- 1ty with which calories are supplied.

The fact has not been overlooked that the inert residuals of the reaction will accumulate upon the upper surface of the receding charge; but the final temperature, if the in-put of energy remains constant, will automatically rise to meet the additional obstruction.

After the zinc has been adequately exhausted, the extraction-ports 23 and 24 are opened when the residuum can be quickly withdrawn, as by means of rakes or hoes. During this operation, it is preferable to close the condenser-vent, or the fume-throat, thereby avoiding the displacement of residual zinc-fume within the chamber and preventing what wduld be a deleterious circulation of air toward and through the condenser.

As stated at the outset of this specification, if a high-grade of roasted concentrate is used, especially if igneously produced, the reducing chamber may be successively charged in bulk; or the supply may be added sister is wholl" immersed all of its heat flows into the charge except only thet which to atmosphere from the terminals. The"l1fe of the resistor, when formed and treated in the manner herein edvertecl to, is unknown; sullice it to say that its cost, as an element oi? lip-keep, is prol'iably as neg eligible a quantity as an incandescent carbon lilun'ient in exhausted glass sphere.

lt goes Without sayingthat various modilficutione can readily be made in the clepicted design RS a Whole, and also in its various elemental details, Without evasion otthe generic principlesherein set forth in sr'iplitude end. summarized in the claims.

ll clsiin 1. An electric frurnece for reducing xiclizetl zinc concentrates by carbon (Zn@+C:Zn-l-CU), comprising a zig-zug resistor the surtaces of which are relatively electrically non-conductive, unmune to OX1 (lotion end no-nrazictii'e. with carbon sus-' zillel limbs, and 5, deflector having a plurality of transverse ports sustained. in the mp per portion otthe resistor space 3. An electric furnace for reducing oxidized zinc concentrates by carbon (ZnO l-C znfl-CO) o having a. reaction chamber, at zig-zag carbon resistor sustained in said chamber and a plurality of extraction ports in the side-Walls of the furnace,

disposed along the lower horizontal zone of said chamber, through which the inert prodnets of the reaction may be Withdrawn.

l. An electric furnace for reducing OXldlZBd zinc concentrates by carbon (Zn(l+O:Zn+CO) having a reaction chamber, av zig-zag, osrbon resistor, immune to superficial reactive attack sustained in said chamber whereby the heat is transferred direct conduction, by radiation, and by re fraction, substantially as hercinbefore set forth.

5. An electric furnace for reducing oxidized zinc concentrates by carbon (ZnO+C:Zn+GO) having a reeellbn chamber, a, zigzag; carbon resistor, having a, plurality of limbs and sustained Within said chamber a, ported deflector Within the chamber, and a fume-throat leading from the reaction chamber to a condenser, said. parts being disposed so that portions of the voletilized products of reaction, when the furnace is charged, Will. escape upwardly from beneath the charge between the limbs of the resistor, through the ports of the (lefiector and finally to the said fumegthroat.

This specification. signed this 21st (layof January, A, 1)., 1919.

JGHN THOMSON Witnesses:

J. lit. AoNsW, lvl. BUnNs'rEIN,

. to e reactive charge Within the chamber by 

